From ebb10f3256067c6e4ebea9a21a92d0199ac7fdf9 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Fri, 12 Jan 2024 07:11:46 -0500
Subject: Fix null pointer issue on array copy

---
 fuzz/CMakeLists.txt        |   4 +++-
 fuzz/qpdf_extra/65681.fuzz | Bin 0 -> 60590 bytes
 fuzz/qtest/fuzz.test       |   2 +-
 libqpdf/QPDF_Array.cc      |   3 +++
 qpdf/qpdf.testcov          |   1 +
 qpdf/qtest/many-nulls.test |   6 +++++-
 qpdf/test_driver.cc        |  12 +++++++++++-
 7 files changed, 24 insertions(+), 4 deletions(-)
 create mode 100644 fuzz/qpdf_extra/65681.fuzz

diff --git a/fuzz/CMakeLists.txt b/fuzz/CMakeLists.txt
index db9bfd71..df1fa807 100644
--- a/fuzz/CMakeLists.txt
+++ b/fuzz/CMakeLists.txt
@@ -109,7 +109,9 @@ set(CORPUS_OTHER
   28262.fuzz
   30507.fuzz
   37740.fuzz
-  57639.fuzz)
+  57639.fuzz
+  65681.fuzz
+)
 
 set(CORPUS_DIR ${CMAKE_CURRENT_BINARY_DIR}/qpdf_corpus)
 file(MAKE_DIRECTORY ${CORPUS_DIR})
diff --git a/fuzz/qpdf_extra/65681.fuzz b/fuzz/qpdf_extra/65681.fuzz
new file mode 100644
index 00000000..7892f7c0
Binary files /dev/null and b/fuzz/qpdf_extra/65681.fuzz differ
diff --git a/fuzz/qtest/fuzz.test b/fuzz/qtest/fuzz.test
index 26995dac..adce995c 100644
--- a/fuzz/qtest/fuzz.test
+++ b/fuzz/qtest/fuzz.test
@@ -20,7 +20,7 @@ my @fuzzers = (
     ['pngpredictor' => 1],
     ['runlength' => 6],
     ['tiffpredictor' => 1],
-    ['qpdf' => 53],             # increment when adding new files
+    ['qpdf' => 54],             # increment when adding new files
     );
 
 my $n_tests = 0;
diff --git a/libqpdf/QPDF_Array.cc b/libqpdf/QPDF_Array.cc
index c8cfe110..7d6f4539 100644
--- a/libqpdf/QPDF_Array.cc
+++ b/libqpdf/QPDF_Array.cc
@@ -1,5 +1,6 @@
 #include <qpdf/QPDF_Array.hh>
 
+#include <qpdf/QTC.hh>
 #include <qpdf/QPDFObjectHandle.hh>
 #include <qpdf/QPDFObject_private.hh>
 
@@ -74,8 +75,10 @@ QPDF_Array::copy(bool shallow)
     if (shallow) {
         return do_create(new QPDF_Array(*this));
     } else {
+        QTC::TC("qpdf", "QPDF_Array copy", sp ? 0 : 1);
         if (sp) {
             auto* result = new QPDF_Array();
+            result->sp = std::make_unique<Sparse>();
             result->sp->size = sp->size;
             for (auto const& element: sp->elements) {
                 auto const& obj = element.second;
diff --git a/qpdf/qpdf.testcov b/qpdf/qpdf.testcov
index 397cbf97..6d0f8a4b 100644
--- a/qpdf/qpdf.testcov
+++ b/qpdf/qpdf.testcov
@@ -692,3 +692,4 @@ QPDF recover xref stream 0
 QPDFJob misplaced page range 0
 QPDFJob duplicated range 0
 QPDFJob json over/under no file 0
+QPDF_Array copy 1
diff --git a/qpdf/qtest/many-nulls.test b/qpdf/qtest/many-nulls.test
index 744075f0..8a723d53 100644
--- a/qpdf/qtest/many-nulls.test
+++ b/qpdf/qtest/many-nulls.test
@@ -29,5 +29,9 @@ $td->runtest("run check file",
              {$td->COMMAND => "qpdf --check a.pdf"},
              {$td->FILE => "many-nulls.out", $td->EXIT_STATUS => 0},
              $td->NORMALIZE_NEWLINES);
+$td->runtest("copy sparse array",
+             {$td->COMMAND => "test_driver 97 many-nulls.pdf"},
+             {$td->STRING => "test 97 done\n", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
 cleanup();
-$td->report(3);
+$td->report(4);
diff --git a/qpdf/test_driver.cc b/qpdf/test_driver.cc
index 2b8eb761..472a96a1 100644
--- a/qpdf/test_driver.cc
+++ b/qpdf/test_driver.cc
@@ -3366,6 +3366,16 @@ test_96(QPDF& pdf, char const* arg2)
     assert(s.unparseBinary() == "<abc0>");
 }
 
+static void
+test_97(QPDF& pdf, char const* arg2)
+{
+    // Shallow array copy. This test uses many-nulls.pdf.
+    auto nulls = pdf.getTrailer().getKey("/Nulls").getArrayItem(0);
+    assert(nulls.isArray() && nulls.getArrayNItems() > 10000);
+    auto nulls2 = nulls.shallowCopy();
+    assert(nulls.unparse() == nulls2.unparse());
+}
+
 void
 runtest(int n, char const* filename1, char const* arg2)
 {
@@ -3467,7 +3477,7 @@ runtest(int n, char const* filename1, char const* arg2)
         {78, test_78}, {79, test_79}, {80, test_80}, {81, test_81}, {82, test_82}, {83, test_83},
         {84, test_84}, {85, test_85}, {86, test_86}, {87, test_87}, {88, test_88}, {89, test_89},
         {90, test_90}, {91, test_91}, {92, test_92}, {93, test_93}, {94, test_94}, {95, test_95},
-        {96, test_96}};
+        {96, test_96}, {97, test_97}};
 
     auto fn = test_functions.find(n);
     if (fn == test_functions.end()) {
-- 
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